a) The speed control of an AC motor can be achieved by using 2 common types of drive circuit, namely the six step and th

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A The Speed Control Of An Ac Motor Can Be Achieved By Using 2 Common Types Of Drive Circuit Namely The Six Step And Th 1 (56.48 KiB) Viewed 19 times

a) The speed control of an AC motor can be achieved by using 2 common types of drive circuit, namely the six step and the PWM types. Describe with the aim of diagrams, the difference between the two types of controller. You should list and explain the power electronic devices used, as well as the details of the DC link for each device. (8 Marks) b) A 25kW, 4-pole induction motor is designed to operate from a 440V, 50Hz, three-phase supply, and when operating at full power on this supply it runs at 1470rpm. The motor efficiency is 92% under both conditions. (i) What supply frequency will be needed to make this motor run at 1270rpm while delivering a shaft power of 12.5kW? (7 Marks) (ii) If the motor were supplied from a sinusoidal variable frequency source, what voltage and current will need to be supplied to it when running at 1365rpm at 12.5kW if the power factor of the motor is 0.85? (10 Marks)